System and method for a TCP mapper

ABSTRACT

A system for congestion control of traffic in a network that uses Transmission Control Protocol (TCP) includes a plurality of TCP congestion control programs having one or more parameters, a plurality of TCP congestion control units running the TCP congestion control programs, and a TCP mapper adapted to map incoming TCP traffic flow from a plurality of incoming TCP traffic flows to the TCP congestion control units based on at least one of (a) the type of application program from which the incoming TCP traffic flow originated (b) the type of network for which the incoming TCP traffic flow is destined, (c) parameters related to network performance (d) network constraints (e) source of the incoming TCP traffic flow, and (f) destination of the incoming TCP traffic flow.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority toU.S. patent application Ser. No. 13/644,057, filed Oct. 3, 2012, whichis hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

This invention is directed towards networks that use the TransmissionControl Protocol (TCP).

SUMMARY

In accordance with one embodiment, a system is provided for congestioncontrol of traffic in a network that uses Transmission Control Protocol(TCP), and the traffic includes a plurality of incoming TCP trafficflows. The system includes a plurality of TCP congestion controlprograms having one or more parameters, a plurality of TCP congestioncontrol units each of which runs one of the plurality of TCP congestioncontrol programs, and a TCP mapper adapted to map a first incoming TCPtraffic flow from the plurality of incoming TCP traffic flows to a firstone of the plurality of TCP congestion control units running a first oneof the plurality of TCP congestion control programs. The mapping isbased on at least one of:

(a) the type of application program from which the incoming TCP trafficflow originated,

(b) the type of network for which the incoming TCP traffic flow isdestined,

(c) parameters related to network performance

(d) network constraints,

(e) source of the incoming TCP traffic flow, and

(f) destination of the incoming TCP traffic flow.

The incoming TCP traffic may originate from a TCP sending host.

One implementation includes a TCP sending host that adjusts the roundtrip time (RTT) seen by that host, and analyzes measurements of theparameters related to network performance, the measurements beingperformed by at least one of the TCP mapper and external sensors. Thesystem may perform one or more heuristics and tune at least oneparameter of the first TCP congestion control program based on resultsof the one or more heuristics. The heuristics may include at least oneof (a) determining presence and persistence of congestion, (b)determining goodput as a fraction of the rate of the traffic transmittedby the TCP host, (c) determining changes in the one-way delays oftraffic transmitted by the TCP host, and (d) estimating channel capacityusing at least one of (i) inter-packet arrival time, (ii)inter-acknowledgement message arrival time, (iii) variance of latency ofpackets within a burst, and (iv) loss rate of packets within a burst.This system may also identify the cause of a packet loss event based ondetermining of presence and persistence of congestion.

In a system that includes a TCP sending host, the TCP mapper may sendsignals to the TCP host, and at least one of those signals may repeatre-transmission of a lost packet.

A method is provided for congestion control of traffic in a network thatuses Transmission Control Protocol (TCP), wherein the traffic includesone or more incoming TCP traffic flows. The network includes a pluralityof TCP congestion control programs and a plurality of TCP congestioncontrol units, each TCP congestion control unit running one of theplurality of TCP congestion control programs. The method maps anincoming TCP traffic flow from the one or more incoming TCP trafficflows to a first of the plurality of TCP congestion control programsusing a TCP mapper. The mapping is based on at least one of

(a) the type of application program from which the incoming TCP trafficflow originated,

(b) the type of network for which the incoming TCP traffic flow isdestined,

(c) parameters related to network performance,

(d) network constraints,

(e) source of the incoming TCP traffic flow, and

(f) destination of the incoming TCP traffic flow.

In one implementation, the TCP mapper is a midstream TCP proxy.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings.

FIG. 1 shows a typical network with one TCP sending host and one TCPreceiving host.

FIG. 2 shows the network of FIG. 1, but with a TCP mapper included.

FIG. 3 shows the network 103 with TCP mappers 105 and 205 at the sendingand receiving side of the network.

FIG. 4 shows another embodiment, whereby sending TCP hosts 201A to 201Mare connected to one mapper.

FIG. 5 shows an embodiment, whereby sending host-mapper combinations401A to 401K are connected to network 103.

FIG. 6 shows an example with sending-host mapper combinations 501A to501L wherein combinations 501A to 501K are single sending host-mappercombinations; and combination 501L is a multiple sending host-mappercombination.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Although the invention will be described in connection with certainpreferred embodiments, it will be understood that the invention is notlimited to those particular embodiments. On the contrary, the inventionis intended to cover all alternatives, modifications, and equivalentarrangements as may be included within the spirit and scope of theinvention as defined by the appended claims.

FIG. 1 shows a typical network, with a TCP sending host 101 sendingtraffic using TCP over a network 103 to a TCP receiving host 102. TheTCP sending host 101 has a TCP transmission queue 104. Network 103 couldbe, for example a single wired, 3G, 4G or Wi-Fi network. In oneembodiment, network 103 could further contain wired, 3G, 4G or Wi-Fisubnetworks.

FIG. 2 shows the network of FIG. 1, but with a TCP mapper 105 included.The TCP mapper 105 acts as a midstream TCP proxy for TCP streams thatwould normally terminate on the TCP receiving host. The TCP mapper 105contains a processing system 107. TCP mapper 105 intercepts incoming TCPtraffic flows from the TCP sending host 101, and the processor 106within a TCP mapper processing system 107 maps each incoming TCP trafficflow to one of the TCP congestion control (CC) units 108-A to 108-N inthe TCP mapper processing system 107. In one embodiment, each CC unitruns a different congestion control program. In another embodiment, asubset of the CC units may run the same program, but each CC unit withinthat subset can only tune or configure a given subset of parameters usedwithin the program. In another embodiment, the TCP mapper processor 106works together with each CC unit to tune the parameters available to theCC unit for the corresponding TCP congestion control program run by theCC unit. Examples of CC programs are provided below. Each CC unit alsohas an associated buffer, 109-A to 109-N as shown in FIG. 2, used tostore packets awaiting transmission. In one embodiment, the TCP mapper105 has several sensors (not shown) to, for example, measure parametersrelating to network performance, such as loss, throughput, latency,bandwidth, jitter and goodput. In another embodiment, the TCP mapperfurther uses these parameters to perform analyses. As will be furtherdetailed below, in another embodiment the TCP mapper performs mappingbased on whether network constraints, for example prioritization andtraffic policing, are being applied in the network.

The TCP mapper 105 provides several advantages. The sending host 101 hasto progress through one or more different stages before reaching thestage corresponding to maximum throughput. Additionally, the speed ofprogression through the stages depends on the round trip time (RTT). Inone embodiment, the mapper 105 is separate but closely located to thesending host 101. In one embodiment, the RTT between the mapper 105 andsending host 101 is below a threshold RTT_(thresh), which is a fractionof the RTT between the sending host 101 and the receiving host 102.RTT_(thresh) can be set, for example, via analysis of historicalrecords, calculation, or simulation of network performance. Since themapper 105 is positioned close to the sending host 101, interception bythe mapper 105 has the effect of reducing the RTT seen by the sendinghost 101, and therefore speeding up the throughput progression of theTCP sending host 101 through the various stages before reaching thestage corresponding to maximum throughput.

In another embodiment, the TCP mapper adjusts the RTT to a value whichis optimally suited to the requirements of the sending host 101. Forexample, the mapper may adjust the RTT so as to reduce the variance ofthe RTT seen by the sending host 101. Alternatively, the mapper mayincrease the RTT by adding in extra delays, as some sending host 101applications perform better when these applications see increased RTT.This is useful, as some operating systems limit the amount ofunacknowledged data if a low RTT is measured.

In a further embodiment, the TCP mapper makes adjustments so as tocontrol the calculation of RTT. For example, the starting value andending value to calculate RTT are adjusted by the mapper as to avoid any“overhead” of sending and receiving the packets respectively at thesending host. In another embodiment, the TCP mapper measures theseoverheads or communicates with the sending host to measure theseoverheads, and subtracts these measures from the recorded RTT. Thisgives a truer estimate of the RTT within the network.

In another embodiment, the TCP mapper is placed within the sending host101, but separate from the sending host 101 TCP engine. This has theeffect of reducing the RTT to nearly zero and further speeding up theprogression of the sending host through the TCP stages to reach thestage where maximum throughput can be achieved. In yet anotherembodiment, the TCP mapper replaces the sending host 101 TCP engine.

The TCP mapper 105 can recognize the application from which the trafficoriginates, such as, for example, including but not limited to, filetransfer traffic, Remote Desktop Protocol (RDP) traffic, or streamingtraffic. In one embodiment, the TCP mapper recognizes the originatingapplication by inspecting packet headers and contents. In anotherembodiment, the TCP mapper recognizes the originating applicationthrough explicit notification by an application, end system or othernetwork device.

In one embodiment, the TCP mapper 105 maps traffic to correspondingcongestion control units, based on the originating application, andstores the packets from the different applications in one of the buffers109A to 109N corresponding to the chosen congestion control unit.

In another embodiment, the TCP mapper is able to determine the type ofnetwork that the traffic is destined for, by, for example, inspectingpacket headers or contents to determine destination, and recognizing thetype of network, for example, wired, 3G, 4G or Wi-Fi that it is destinedfor. Then, the TCP mapper maps traffic to CC units 108A to 108N based onthe type of network that the traffic is destined for. For example, therecould be different CC units corresponding to wired, 3G, 4G or Wi-Finetworks.

In another embodiment, the TCP mapper is aware of the congestion controlprogram used by other TCP flows flowing through a common network device.Then the mapping to CC units 108A to 108N is dependent upon thecongestion control program used by these other flows. For example, ifthe TCP mapper needs to map traffic from an incoming flow, anddetermines that many of the other incoming flows are sent by hosts usingthe TCP Reno program, then the TCP mapper may map the traffic from theincoming flow to the TCP CUBIC program.

The TCP mapper can determine the other congestion control programs beingused in the network in a variety of ways. In one embodiment, the TCPmapper can correlate congestion window size evolution of an unknowncongestion control program to that of an existing congestion controlprogram, based on the known behaviour of the congestion control program.

In another embodiment, the TCP mapper samples the evolution of theinflight window, which is the amount of bytes in flight for a given RTT;and detects that this value is linearly increasing with time, assumingdiscrete RTT-sized time increments. Based on this, the TCP mapperdecides with reasonable accuracy that the TCP RENO congestion controlprogram is being used.

In another embodiment, the TCP mapper uses higher sampling rates, tosample the evolution of the inflight window, and determines that theshape of the curve between loss events is that of a cubic function,biased in time and amplitude. Based on this, the TCP mapper decides withreasonable accuracy that the TCP CUBIC congestion control program isbeing used.

In another embodiment, the TCP mapper uses known methods for identifyingcongestion control programs based on probing methods (see e.g.“Identifying TCP Congestion Control Mechanisms using Active Probing” byS. S. Feyzabadi located athttp://cnds.eecs.jacobs-university.de/courses/nds-2009/feyzabadi-report.pdf).

In another embodiment, after deducing the TCP congestion control programbeing used by a host, the TCP mapper further determines whether it issuitable for flows originating from that host given current observednetwork conditions. If not, the TCP mapper maps such flows to a moreappropriate congestion control program.

In another embodiment, the TCP mapper maps traffic to CC units 108A to108N based upon either the source or the destination of the flow towhich the traffic belongs. The TCP mapper is able to identify the sourceor the destination by, for example, inspecting packet headers andcontents; or via explicit notification by an application, end system orother network device.

In yet another embodiment, the TCP mapper maps traffic to CC units 108Ato 108N based upon measurements of parameters relating to networkperformance such as loss, throughput, goodput, latency, packet jitterand bandwidth. In one embodiment, these parameter measurements are takenby sensors within the TCP mapper 105. However, certain parameters mayonly be measured at the receive side, so in another embodiment, thesenetwork performance are measured externally, for example, by externalsensors at the receive side, and conveyed to the TCP mapper 105 viaeither in-band or out-of-band techniques.

In another embodiment, the TCP mapper uses these measurements to performanalyses, and makes mapping decisions based on the results of theseanalyses. For example, the TCP mapper could use these measurements todetermine if a network is congested, and the nature of the congestion,in the following way: When the aggregate bitrate of all the flows in agiven channel reaches the limits of the channel capacity, the channel issaid to be congested. The persistence of this congestion can bedetermined by analyzing the resulting steady-state and mapping out theevolution of loss and latency over time; as well as the correlationbetween the two. In another embodiment, heuristic techniques orheuristics such as the techniques described above are performed by anexternal module. Then, based on the results of these analyses, the TCPmapper maps traffic to one of the CC units.

In yet another embodiment, the TCP mapper maps traffic to CC units 108Ato 108N based upon network constraints such as prioritization of certaintypes of traffic over other types of traffic with the network; and thepresence of traffic policing. In one embodiment, the TCP mapper canauto-detect the presence of such constraints. For example, the TCPmapper is able to detect if prioritization is being used by looking atvarious aspects of the packets such as Internet Protocol DifferentiatedServices Code Point (IP DSCP) bits or looking at the priority bits inthe Media Access Control (MAC) headers. The TCP mapper is also able todetect when a given TCP stream is “application-limited,” or in otherwords, not utilizing the maximum bandwidth allowed by the current stateof the CC program. By analyzing if the flow in question is “applicationlimited” or is being limited by prioritization policies, the TCP mappercan choose an appropriate CC program. Alternatively, the TCP mapper canbe explicitly programmed to take into account these network constraints.For example, the mapper may be programmed by a user to recognize thatcertain types of traffic will be prioritized over other types oftraffic. Similarly, relevant data can be extracted from policingcontracts by a user and then explicitly programmed into the TCP mapperby a user. Mapping decisions are then made based on this data.

In a further embodiment, the TCP mapper maps traffic to CC units 108A to108N based upon two or more of

-   -   originating application;    -   the type of network that the traffic is destined for;    -   source of the flow to which the traffic belongs;    -   destination of the flow to which the traffic belongs;    -   parameters related to network performance    -   network constraints

As explained previously, in one embodiment, each CC unit runs adifferent congestion control program. In another embodiment, a subset ofthe CC units may run the same program, but each CC unit within thatsubset can only tune or configure a given subset of parameters usedwithin the program. In another embodiment, the TCP mapper processor 106works together with each CC unit to tune the parameters available to theCC unit for the corresponding TCP congestion control program run by theCC unit.

The mapping can be carried out in a variety of ways. In one embodiment,a lookup table can be used to map TCP port numbers to CC units with adefined default CC unit being used in the case that no lookup tableentry exists. Other lookup tables could map source and destination IPaddresses and other IP and TCP header values to target CC units. Inanother embodiment, multiple lookup tables can be used in order until amatch is found.

As explained previously, each congestion control unit is able to tunethe parameters available to the CC unit for the congestion controlprogram which is run by the CC unit on the fly, such that theconstraints for each flow type (latency, bandwidth, jitter) are met. Asan example, if the CC unit is using the TCP CUBIC, the reference timeconstants and overall scaling factors can be the adjusted parameters.Multiple tuning approaches can be used. In one embodiment, tuning can bebased on measurements of parameters relating to network performance suchas loss, throughput, goodput, latency, packet jitter and bandwidth. Alookup table containing measured network performance-related metrics andtuning parameters can be used. These metrics can include packet loss,latency, jitter, throughput, goodput and other measurable networkstatistics. In another embodiment, a lookup table relating internal CCmetrics such as buffer fill level and timer values to tuning parameterscan be used. In another embodiment, the TCP mapper processor 106co-operates with each CC unit to tune the parameters available to the CCunit for the corresponding TCP congestion control program run by the CCunit, such as in the TCP CUBIC example given above. Initial parametervalues can be calculated based on historical measurements and thenfurther tuned as new measurements are made.

In another embodiment, the TCP mapper uses these measurements to performanalyses, and performs tuning based on the results of the analyses. Aspreviously explained, the TCP mapper may, for example, use thesemeasurements to determine if the network is persistently congested. TheTCP mapper can then perform tuning accordingly.

In another embodiment, the TCP mapper uses other heuristics toappropriately tune the parameters. Measures such as achieved goodput,bottleneck link buffer capacity and channel capacity are analyzed, andused in such heuristics. The results from use of the heuristics areutilized to tune the parameters. In one embodiment, the heuristics areperformed by an external module.

In yet another example, heuristics are used to differentiate betweennetwork loss due to a congestion event and due to a random event.Referring to the example of congestion, once the onset of a period ofpersistent congestion has been identified, it is highly likely thatpacket loss events during this period of persistent congestion are dueto congestion rather than random causes, and can be identified as such.Similarly, during a period of non-congestion, loss events are morelikely to be random events. Based on the results obtained from applyingthis heuristic, the mapper performs tuning of the parametersaccordingly. As an example, in one embodiment if one of the parametersis a congestion window and the loss event is determined to be a randomevent rather than due to congestion, then the mapper sends aninstruction to the CC program to not reduce the congestion window.

Another example of a heuristic is measuring the rate of the TCP trafficacknowledged by the receiving host, that is, the goodput, as a fractionof the rate of the TCP traffic transmitted by the sending host. Thisratio is then referred to a lookup table to choose an appropriate tuningparameter. This is performed, for example, to prevent overflow ofnetwork buffers. The lookup table is built, for example, usinghistorical observations, computer simulations, or by usingwell-established mathematical relationships for known traffic arrivalprocesses such as Poisson processes.

Another example of a heuristic is using measurements of the changes inthe one-way delays of data transmitted, to estimate the number of queuedpackets in a bottleneck link buffer. Similar to the previous example,the changes in the one-way delays are referred to a lookup table toestimate the number of queued packets in a bottleneck link buffer. Sucha lookup table is built, for example, by using historical observations;computer simulations; or well-established mathematical relationships forknown traffic arrival processes such as Poisson processes. Thisheuristic assists in limiting the “bloat” in latency caused by packetswaiting in long queues in bottleneck link buffers.

A further example of a heuristic is using inter-packet arrival time toestimate channel capacity. Inter-acknowledgement message arrival timemay also be used to estimate channel capacity. The variance of latencyof packets within a burst may be used to estimate channel capacity. Lossrate of packets within a burst may also be used to estimate channelcapacity. One or more of:

-   -   Inter-packet arrival time    -   Inter-acknowledgement message arrival time    -   Variance of latency of packets within a burst    -   Loss rate of packets within a burst        may also be used to estimate channel capacity. Similar to the        previous example, one or more of these measures can be referred        to a lookup table to estimate the channel capacity. The lookup        table is built using, for example, historical observations,        computer simulations, or well-known mathematical relationships.        Such estimations may be used to ensure that the average traffic        rate is appropriately matched to the estimated link capacity.

In another embodiment, tuning can be based upon network constraints, forexample, prioritization of certain types of traffic over other types oftraffic within the network. As explained previously, the TCP mapper isable to auto-detect if constraints such as prioritization are beingused. Alternatively, the TCP mapper can be explicitly programmed by auser to take constraints into account when performing mapping. Aspreviously explained, the mapper can be programmed to take into accountthe prioritization of certain types of traffic will be prioritized overother types of traffic. Similarly, relevant data can be extracted frompolicing contracts by a user and then explicitly programmed into the TCPmapper by the user. Tuning decisions are then made based on this data.

In another embodiment, as previously explained, the TCP mapper is awareof the congestion control programs used by other TCP flows flowingthrough a common network device. The mapper is able to identifycongestion control programs using various approaches, as outlined above.Then, the mapper can perform tuning based on the other congestioncontrol programs being used in the network.

In another embodiment, the mapping to a CC unit for a given flow couldbe switched “on the fly” by the TCP mapper 105 based on networkperformance measurements. Consider a situation where a flow is currentlymapped to a first CC unit. The mapping can then be dynamically switched,such that congestion control for traffic belonging to the same flow willthen be handled by a second CC unit, different from the first CC unit.After the dynamic switching, the traffic belonging to the flow will bebuffered in the buffer corresponding to the second CC unit. This can beaccomplished by copying the data from the buffer of the first CC unit tothe buffer of the second CC unit and using the latest known metrics tocalculate the initial settings for the parameters available to thesecond CC unit. In one embodiment, the TCP mapper processor 106dynamically switches the flow mapping to the second CC unit and copiesthe traffic belonging to the flow from the first CC unit to the bufferof the second CC unit. The second CC unit calculates the initialsettings for the parameters available to it. In a further embodiment,the TCP mapper processor 106 co-operates with the second CC unit tocalculate the initial settings for the parameters.

Another approach is for the TCP mapper processor 106 to co-operate withthe first CC unit to tune the parameters available to the first CC unitfor the CC program being run by the first CC unit; while the TCP mapperprocessor 106 concurrently co-operates with alternate CC units to tuneavailable parameters for the CC programs run by the alternate CC units.This way, the correct settings for the parameters are already in placewhen a switch to an alternate CC unit is desired.

Congestion control program parameter tuning is performed based on, forexample, network performance measurements such as loss, throughput,goodput, latency, packet jitter and bandwidth. As explained previously,in one embodiment, these network performance measurements are taken bysensors within the TCP mapper 105. As explained previously, certainnetwork performance measurements may only be measured at the receiveside, so in another embodiment, these network performance measurementsare measured externally, for example, by external sensors at the receiveside, and conveyed to the TCP mapper 105 via either in-band orout-of-band techniques.

In one embodiment, the TCP mapper processor 106 collects the resultsfrom the sensors, and distributes these results to the individual CCunits 108A to 108N. At each CC unit, parameters for the TCP congestioncontrol program run by the unit are tuned on the fly by the CC unitbased on different application requirements and parameters related tonetwork performance. In another embodiment, the TCP mapper processor 106works together with each CC unit to tune the parameters for thecorresponding TCP congestion control program run by the CC unit.

Various types of TCP congestion control programs can be run. In oneembodiment, one of the CC units 108A to 108N runs the TCP Hybla CCprogram. Then, traffic to be transmitted to networks with long RTTs forexample, much greater than 500 ms, is directed to the buffer associatedwith the TCP Hybla CC unit, and the corresponding TCP Hybla CC unit willbe used for congestion control for this traffic. The operation andtuning of relevant parameters in the TCP Hybla CC unit has been welldocumented elsewhere (see, for example, C. Caini et al, “TCP Hybla: aTCP Enhancement for Heterogeneous Networks,” in International Journal ofSatellite Communications and Networking, John Wiley & Sons, Volume 22,Number 5, pp 547-566, September 2004)

In another embodiment, one of the CC units 108A to 108N runs the TCPCUBIC congestion control program. Then, for example, traffic to betransmitted to a high speed network, is directed to the bufferassociated with TCP CUBIC, and the corresponding TCP CUBIC CC unit willbe used for congestion control for this traffic. The operation andtuning of relevant parameters in the TCP CUBIC CC unit has been welldocumented elsewhere (see, for example, Ha et al “CUBIC: A NewTCP-Friendly High-Speed TCP Variant” ACM SIGOPS Operating System Review,Volume 42, Issue 5, July 2008, Page(s):64-74, 2008.)

In another embodiment, one of the CC units 108A to 108N runs the DataCenter TCP (DCTCP) congestion control program. Then, for example,traffic to be transmitted to a data center network; or traffic fromapplications requiring low latency and high bandwidth; is directed tothe buffer associated with DCTCP. The corresponding DCTCP CC unit willbe used for this traffic. The operation and tuning of relevantparameters in the DCTCP CC unit has been well documented elsewhere (see,for example, Alizadeh et al “DCTCP: Efficient Packet Transport for theCommoditized Data Center”, Proceedings of SIGCOMM 2010)

In another embodiment, one of the CC units 108A to 108N runs the TCPWestwood+ congestion control program or the TCP Westwood CC program.Then, for example, traffic to be transmitted to a wireless network isdirected to the buffer associated with TCP Westwood+ or TCP Westwood.The corresponding TCP Westwood+CC unit will then be used for congestioncontrol for this traffic. The operation and tuning of relevantparameters has been well documented elsewhere (see, for example, Mascoloet al “TCP Westwood: Bandwidth Estimation for Enhanced Transport overWireless Links” Proc. of the ACM Mobicom 2001, Rome, Italy, July 16-212001; or Grieco et al “Performance evaluation and comparison ofWestwood+, New Reno and Vegas TCP congestion control” ACM ComputerCommunication Review, April 2004, Vol. 34(2))

In another embodiment, one of the CC units 108A to 108N runs the TCPIllinois congestion control program or the TCP Illinois CC program.Then, for example, traffic to be transmitted to a high speed, long RTTnetwork is directed to the buffer associated with TCP Illinois. Thecorresponding TCP Illinois CC unit will then be used for congestioncontrol for this traffic. The operation and tuning of relevantparameters has been well documented elsewhere (see, for example, Liu etal, “TCP-Illinois: A loss and delay-based congestion control algorithmfor high-speed networks” Pages 417-440, Performance Evaluation 65(2008))

In another embodiment, one of the CC units 108A to 108N runs the FASTTCP CC program. Then, for example, traffic from applications which arelatency and jitter sensitive; or to be transmitted to a high-speed, longRTT network; is directed to the buffer associated with FAST TCP. Thecorresponding FAST TCP CC unit will then be used for congestion controlfor this traffic. The operation and tuning of relevant parameters hasbeen well documented elsewhere (see, for example, Wei et al “FAST TCP:Motivation, Architecture, Algorithms, Performance”, IEEE/ACMTransactions on Networking, vol. 14. no. 6 Dec. 2006)

Other types of CC programs can be run on the CC units. For example, a CCprogram which dynamically modifies window sizes based on measuredlatency can also be run on one of the CC units 108A to 108N. Then, forexample, traffic from applications such as Remote Desktop Protocol (RDP)can be directed to the corresponding buffer, and the CC unit will beused for congestion control for this type of traffic.

In one embodiment, the TCP mapper 105 can also perform flow adaptationby sending signals to the sending host so as to, for example:

-   -   control the throughput progression    -   avoid the overflow of the buffers in the mapper    -   reduce latency due to buffering.    -   explicit request to change congestion control program        These steps can include, but are not limited to, one or more of        the following:    -   reducing the sending rate of traffic by altering timestamps,    -   simulating discard of TCP segments,    -   modifying window sizes,    -   modifying scaling parameters, and    -   slowing the transmission of ACKs.        The TCP mapper can also send signals to the sending host to        adjust TCP options such as those documented in Internet        Engineering Task Force (IETF) Request for Comments (RFC) 2780        “IRNA Allocation Guidelines For Values In the Internet Protocol        and Related Headers” by S. Bradner and V. Paxson, March 2000.

When a lost packet is re-transmitted, and selective acknowledgements(SACKs) corresponding to the packets transmitted after there-transmitted packet are received by the sending host, it is highlylikely that the re-transmitted packet is also lost. In anotherembodiment, the TCP mapper 105 can send signals to the sending host torepeat the re-transmission.

In one embodiment, as shown in FIG. 3, there are TCP mappers 105 and 205at the sending and receiving side of the network 103 respectively. Then,the sending and receiving mappers 105 and 205 can interact with eachother to ensure that the constraints for the various flow types are met.In one embodiment, the receive side TCP mapper 205 can perform the flowadaptation steps outlined above. In another embodiment, both the sendside and receive side TCP mappers 105 and 205 perform the flowadaptation steps outlined above. In yet another embodiment, only eitherthe send side TCP mapper 105 or the receive side TCP mapper 205 performsthe flow adaptation steps outlined above.

As explained previously certain network performance measurements,including, but not limited to, for example, packet jitter and bandwidth,may only be measured at the receive side. In one embodiment, the sensorsin the receive side TCP mapper 205 are used to measure these parameters.Then, the receive side TCP mapper 205 communicates with the send-sidemapper 105 using either in-band or out of band techniques. Networkperformance measurements which could be measured by the receive side TCPmapper 205 include, but are not limited to, received bandwidth of theassociated stream, total bandwidth being received (sum of all receivedstreams), packet jitter, bit error rate, packet error rate andinter-packet spacing. Other useful information which could be useful totune the send-side TCP mapper 105 can be exchanged.

Other information can be exchanged using in-band or out of bandtechniques. For example, information on type of subnetworks found innetwork 103, for example WiFi, 3G and wired; downstream networkfailures; queueing delays and so on, can be transmitted.

In one embodiment, the TCP mapper 105 at the sending side has 2 modes ofoperation:

-   -   “Single-ended”—where there is no corresponding TCP mapper 205 at        the receive side    -   “Dual-ended” where there is a corresponding TCP mapper 205 at        the receive side

In one embodiment, the send side TCP mapper in dual-ended mode isfurther configured to summarize one or more TCP acknowledgements into asingle TCP acknowledgement. This is beneficial in networks where sendingmultiple acknowledgements could reduce network performance. In anotherembodiment, the receive side TCP mapper is able to take in a single TCPacknowledgement, derive one or more TCP acknowledgements from the singleTCP acknowledgement, and transmit the one or more derived TCPacknowledgements from the single TCP acknowledgement. In one embodiment,both the summarization and derivation are carried out within one of theTCP congestion control programs.

FIG. 4 shows another embodiment, whereby sending TCP hosts 201A to 201Mare connected to the same mapper 305. In this case, the mapper 305aggregates and processes flows from several different hosts. This couldcorrespond to, for example, an office.

FIG. 5 shows yet another embodiment, whereby there are several sendinghost-mapper combinations 401A to 401K. Host-mapper combination 401Acontains TCP sending host 401AA and mapper 401AB; host-mappercombination 401B contains TCP sending host 401BA and mapper 401BB; andso on until host mapper combination 401K, which contains TCP sendinghost 401KA and mapper 401KB. The mappers 401AA-401KA are connected tocontrol network 411 and can interact with each other. In one embodiment,the mappers 401AA-401KA interact with each other in a decentralizedmanner. In another embodiment, there is centralized control, forexample, one of the mappers 401AA-401KA is considered a master mapper.In another embodiment, the processor in the master mapper additionallyplays the role of co-ordinating the operation of the other mappers. Inanother embodiment, centralized control is provided by a dedicatedsystem, separate from the TCP mappers. In one embodiment, this dedicatedsystem could reside within control network 411. In another embodiment,this dedicated system could be outside of control network 411.

Further combinations are also possible. One “hybrid” example is shown inFIG. 6, where there are several sending-host mapper combinations 501A,501B . . . 501K, SOIL. The sending host-mapper combinations 501A to 501Keach contain a TCP sending host and a mapper. Host-mapper combination501A contains TCP sending host 501AA and mapper 501AB; host-mappercombination 501B contains TCP sending host 501BA and mapper 501BB; andso on until host mapper combination 501K, which contains TCP sendinghost 501KA and mapper 501KB.

However, host-mapper combination 501L is a multiple sending host-singlemapper combination, similar to that of FIG. 4. Mapper 501LB is connectedto sending hosts 501LA-A to 501LA-M. While only one multiple sendinghost-single mapper combination is shown, in other embodiments there aremore than one multiple sending host-single mapper combinations present.

The configurations shown in FIGS. 4, 5 and 6 can also be implemented onthe receiving side. Similar to that of FIG. 4, a single TCP mapper canbe connected to several receiving hosts. Similar to FIG. 5, there may beseveral receiving host-mapper combinations. Similar to FIG. 6, there maybe several receiving host-mapper combinations, and one or more of thesecombinations may contain multiple receiving hosts. The TCP mappers atthe sending side can then be set to one of the 2 modes previouslydescribed.

In yet another embodiment, the TCP mappers can also inter-operate withother TCP control devices within the network. The control devices andTCP mappers exchange data with each other and use these as inputs foroperations. The control devices may interact with either send-side orreceive-side TCP mappers in configurations where there is only one orthe other; or both send-side and receive-side TCP mappers inconfigurations where there are both.

In another embodiment, referring to FIG. 2, in the event of a subnetworkfailure within network 103, the TCP mapper 105 will continue to receivetraffic from the sending host 101, and store traffic within buffers 109Ato 109N while looking for an alternate path within network 103 to sendtraffic and the individual TCP congestion control programs within mapper105 perform tuning for the alternate path.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

The invention claimed is:
 1. A method for congestion control of trafficin a network that uses Transmission Control Protocol (TCP), wherein saidtraffic includes one or more incoming TCP traffic flows originating fromat least one TCP sending host and destined for at least one receivingdestination, and that includes a plurality of TCP congestion controlprograms and at least one TCP congestion control unit running one ofsaid plurality of TCP congestion control programs, said methodcomprising: terminating, by a TCP mapper acting as a midstream TCPproxy, the one or more incoming TCP traffic flows; processing all of theone or more terminated incoming TCP traffic flows, wherein saidprocessing comprises mapping all of the terminated one or more incomingTCP traffic flows, to one or more of said plurality of TCP congestioncontrol programs using the TCP mapper, and wherein said mapping is basedon a plurality of (a) the type of application program from which thefirst incoming TCP traffic flow originated, (b) the type of network forwhich the first incoming TCP traffic flow is destined, (c) parametersrelated to network performance, (d) network constraints, (e) source ofthe first incoming TCP traffic flow, and (f) destination of the firstincoming TCP traffic flow; and wherein said TCP mapper is connected tosaid at least one TCP sending host over the network, and operates in asingle-ended mode without a corresponding TCP mapper connected to the atleast one receiving destination.
 2. The method of claim 1, furthercomprising adjusting the round trip time (RTT) seen by said at least oneTCP sending host.
 3. The method of claim 1, further comprising said TCPmapper sending signals to said at least one TCP sending host.
 4. Themethod of claim 3, wherein said TCP mapper sends a signal to said atleast one TCP sending host to repeat re-transmission of a lost packet.5. A method for congestion control of traffic in a network that usesTransmission Control Protocol (TCP), wherein said traffic includes oneor more incoming TCP traffic flows, and that includes a plurality of TCPcongestion control programs and at least one TCP congestion controlunit, each of the at least one TCP congestion control unit running oneof said plurality of TCP congestion control programs, said methodcomprising: mapping a first incoming TCP traffic flow, wherein saidfirst incoming TCP traffic flow originates from a TCP sending host, to afirst of said plurality of TCP congestion control programs using a TCPmapper, wherein said mapping is based on a plurality of (a) the type ofapplication program from which the first incoming TCP traffic floworiginated, (b) the type of network for which the first incoming TCPtraffic flow is destined, (c) parameters related to network performance,(d) network constraints, (e) source of the first incoming TCP trafficflow, and (f) destination of the first incoming TCP traffic flow; andwherein said TCP mapper is connected to said at least one TCP sendinghost over the network, and operates in a single-ended mode without acorresponding TCP mapper connected to the at least one receivingdestination.
 6. The method of claim 5, wherein said TCP sending hostcomprises a TCP engine, and said TCP mapper is separate from the TCPengine.
 7. The method of claim 5, wherein said mapping is based onparameters related to network performance; and further comprisinganalyzing measurements of said parameters related to networkperformance, wherein said measurements are performed by at least one ofthe TCP mapper and external sensors.
 8. The method of claim 7, furthercomprising performing one or more heuristics and tuning at least oneparameter of said first TCP congestion control program based on resultsof said one or more heuristics.
 9. The method of claim 8, wherein saidone or more heuristics comprises at least one of determining presenceand persistence of congestion; determining goodput as a fraction of therate of the traffic transmitted by said TCP host; determining changes inthe one-way delays of traffic transmitted by said TCP host; andestimating channel capacity using at least one of inter-packet arrivaltime, inter-acknowledgement message arrival time, variance of latency ofpackets within a burst of packets, and loss rate of packets within aburst of packets.
 10. The method of claim 5, further comprising said TCPmapper sending signals to said TCP sending host.
 11. The method of claim5, further comprising dynamically switching the mapping from the firstTCP congestion control program to a second TCP congestion controlprogram; and tuning at least one parameter of said second TCP congestioncontrol program.
 12. A method for congestion control of traffic in anetwork that uses Transmission Control Protocol (TCP), wherein saidtraffic includes one or more incoming TCP traffic flows, and thatincludes a plurality of TCP congestion control programs and at least oneTCP congestion control units, each of the at least one TCP congestioncontrol unit running one of said plurality of TCP congestion controlprograms, said method comprising: mapping a first incoming TCP trafficflow, said first incoming TCP traffic flow originating from a TCPsending host from said one or more incoming TCP traffic flows to a firstof said plurality of TCP congestion control programs using a TCP mapper,wherein said mapping is based on parameters related to networkperformance; said mapping further comprising analyzing measurements ofsaid parameters related to network performance, wherein saidmeasurements are performed by at least one of the TCP mapper andexternal sensors, performing heuristics comprising determining presenceand persistence of congestion, and identifying the cause of a packetloss event based on the determining of presence and persistence ofcongestion, wherein said identifying comprises correlating the packetloss event to one or more determined periods of persistent congestion;and tuning at least one parameter of said first TCP congestion controlprogram based on results of said one or more heuristics.
 13. The methodof claim 12, wherein said TCP mapper is included within said TCP sendinghost.
 14. The method of claim 12, wherein said determining of presenceand persistence of congestion comprises estimating channel capacityusing one or more of inter-packet arrival time, inter-acknowledgementmessage arrival time, variance of latency of packets within a burst, andloss rate of packets within a burst.
 15. The method of claim 12, furthercomprising dynamically switching the mapping from the first TCPcongestion control program to a second TCP congestion control program;and tuning at least one parameter of said second TCP congestion controlprogram.
 16. The method of claim 12, wherein said determining ofpersistence of congestion further comprises determining the evolution ofloss and latency over time, and determining the correlation between theloss and the latency.
 17. A system for congestion control of traffic ina network that uses Transmission Control Protocol (TCP), said trafficcomprising a plurality of incoming TCP traffic flows originating from aplurality of TCP sending hosts, said system comprising one or more TCPmappers, wherein each of the one or more TCP mappers receives one ormore of the plurality of incoming TCP traffic flows; wherein each TCPmapper is associated with at least one TCP congestion control unit, eachof the at least one congestion control unit running one of a pluralityof TCP congestion control programs, and wherein each TCP mapperdetermines which of the plurality of TCP congestion control programs tomap the one or more received incoming TCP traffic flows to, saiddetermining based on at lest one a plurality of (a) the type ofapplication program from which the incoming TCP traffic flow originated,(b) the type of network for which the incoming TCP traffic flow isdestined, (c) parameters related to network performance (d) networkconstraints, (e) source of the incoming TCP traffic flow, and (f)destination of the incoming TCP traffic flow, and maps the one or morereceived incoming TCP traffic flows to one of said at least oneassociated TCP congestion control unit based on the determined TCPcongestion control program, and further wherein each TCP mapper isconnected to at least one TCP sending host, and at least one of the oneor more TCP mappers is connected to only one TCP sending host.
 18. Thesystem of claim 17, wherein each TCP mapper adjusts the round trip timeseen by the at least one TCP sending host connected to the TCP mapper.19. The system of claim 17, further comprising performing measurementsof one or more parameters related to network performance.
 20. The systemof claim 19, further comprising performing one or more heuristics, andeach TCP mapper tunes at least one parameter of the plurality of TCPcongestion control programs based on one or more results of said one ormore heuristics.
 21. The system of claim 20, wherein said one or moreheuristics comprises at least one of determining presence andpersistence of congestion; determining goodput as a fraction of the rateof the traffic transmitted by said TCP host; determining changes in theone-way delays of traffic transmitted by said TCP host; and estimatingchannel capacity using at least one of inter-packet arrival time,inter-acknowledgement message arrival time, variance of latency ofpackets within a burst of packets, and loss rate of packets within aburst of packets.
 22. The system of claim 16, further comprising eachTCP mapper sending one or more signals to the one or more TCP sendinghosts connected to the TCP mapper.
 23. The system of claim 22, whereinone of the one or more signals is a signal to repeat re-transmission ofa lost packet.
 24. The system of claim 16, further wherein at least oneof the one or more TCP mappers is placed within at least one of theplurality TCP sending hosts.
 25. The method of claim 1, furthercomprising dynamically switching the mapping for a first incoming TCPtraffic flow from a first TCP congestion control program to a second TCPcongestion control program; and tuning at least one parameter of saidsecond TCP congestion control program.
 26. The method of claim 1,wherein the mapping is based on network constraints and parametersrelated to network performance, said network constraints comprising atleast one of prioritization of traffic, and traffic policing.
 27. Themethod of claim 25, further comprising buffering said first incoming TCPtraffic flow in a buffer associated with said second TCP congestioncontrol program.
 28. The method of claim 26, further comprisingauto-detecting, by the TCP mapper, the presence of the networkconstraints.
 29. The method of claim 1, wherein the mapping is based onparameters related to network performance, and the type of applicationprogram from which the first incoming TCP traffic flow originated,further wherein said mapping is based on measuring parameters related tonetwork performance; and analyzing the measurements to determine ifcongestion is present, the analyzing further comprising determining thepersistence of the congestion, comprising determining the evolution ofloss and latency over time, and determining the correlation between theloss and the latency.
 30. The method of claim 29, further comprisingrecognizing, by the TCP mapper, the type of application program fromwhich the first incoming TCP traffic flow originated.